(tr)uSDX Forum

Hi all,

I recently received mt (tr)uSDX, ordered from the AliExpress UpTech store.

I hooked it up to the audio interface of my laptop, using nothing but straight cables, and then used the tuning feature of JTDX to generate a signal. This was sent through an ATU-100 antenna tuning unit for power measurement, into a dummy load. The (tr)uSDX was powered with a 12V USB-C PD trigger module.

Here's the result of the measurement across the bands:

20m: 1.9W
30m: 3.0W
40m: 1.7W
60m: 2.0W
80m: 3.5W

My questions are: Are those typical values? Is especially the huge difference between power output on different bands to be expected? Would I see higher power outputs by supplying more voltage? Might my audio level be too low to achieve the theoretical 5W output, and is there something in the configuration I can tune?

73 de Andreas, DB8GK

The device is pre-assembled and not really adjusted.
Use this guide:

https://www.youtube.com/watch?v=qN7hHsvcNMM

viewtopic.php?p=1686#p1686

Normally you have 4-5 W at 12V if you tune the toroids properly.

Great information, thanks!

By following the coils spacing adjustment on the toroid you may get a benefit, but you may need to add or remove a coil.

how safe is it too unsolder the toroids ?
72
ON6UU

on6uu wrote: ↑05 Jun 2022, 12:17 how safe is it too unsolder the toroids ?

If it smells like fried finger, you should practice it first.

Good soldering skills should be available anyway.
And if you boil out the solder lugs, you've done something wrong.

Power input is very important. In my rig in 40m with 11.6V power is 4,5W and with 13,8V increese to 5,5W

Please tell me what is the maximum power input: Volts / mAh?

Thank you,
Boris

Theoretically should still work with ~15V; I'd try not to put more than the standard 13.8V into it to keep within the safety margins available.

I too am seeing the same issue with a pre-built unit ordered from uellyqh (Sunny) on the eBay "official vendor" page. No criticism of this vendor - they have been incredibly helpful.

I'm using a power supply built with 8 AA cells. Currently measuring 12.12V on no load.

My power output on 40m is 3.2 to 3.4W and on 20m is 5.4 to 6W. A huge difference. SWR on the antenna is about 1.3

This is measured on the internal wattmeter and I have no idea how useful that is. I bought a used QRP wattmeter but it doesn't work! Wildly inaccurate!

I'm newly licensed and brand new to QRP. Any comments useful. I gather it may be a tuning issue on the RF board?

Tnx VA7RLX Ritchie in BC, Canada